The present invention relates to the technology to process an audio signal.
In a hall, a tearoom, and the like, for example, the necessity of providing different sound contents (information, music, etc.) every nearby area arises occasionally. In such case, such a problem comes up that, when the speaker is provided on an each area basis, respective sound contents leak out to the surrounding areas. In the prior art, various measures such as an adjustment in an arrangement of the speakers or a sound volume level of the contents, a provision of a sound insulating wall at a boundary between the areas, and the like have been taken against the above problem.
For example, in Patent Literature 1, the technology called the sound image normalizing system to form a directional acoustic space by a parametric speaker is disclosed. Also, in Patent Literature 2, the technology called the active noise control to reduce a noise by generating the sound that has an opposite phase to the surrounding noise is disclosed. Also, in Patent Literature 3, the technology to reduce a gear noise reaching the inside of a car by utilizing the so-called masking effect, which reduces the noise by generating a sound whose acoustic characteristic is analogous to the noise, is disclosed.    [Patent Literature 1] JP-A-5-345549    [Patent Literature 2] JP-A-7-319479    [Patent Literature 3] JP-A-2005-343401
For example, with respect to the gear noise in Patent Literature 3, the masking sound suitable to mask the noise can be decided previously by specifying the acoustic characteristic in advance. However, in the hall, the tearoom, and the like, since the sound contents are reproduced in answer to a user's desire every area, it is impossible to decide in advance the characteristics, etc. of the masking sound.